but president obama will be at the united nations, telling the assembly of leaders that the united states will do what we must to prevent iran from obtaining a nuclear weapon. a senior administration official tells abc news this morning in new york city, in front of the united nations, president obama will reiterate the u.s. commitment to preventing iran from iracquiring a nuclear weap. and the u.s. will not shrink to justice, those who harm americans. sensing an opening, mtitt romne has been assailing the president for calling the situation bumps in the road. >> we had an ambassador assassinated. and iran is that much closer to building a nuclear weapon. >> reporter: the white house says the president was referring broadly to transformations in the region. >> there's a rather desperate attempt to grasp at words and phrases here, to find political advantage. and in this case, that's profoundly offensive. >> reporter: the romney campaign is also posting to a clip online about the president's "60 minutes" interview, about his campaign ad. >> do we see us going over the mistakes that are mad